Regulation of purE transcription in a purE::lac fusion strain of Escherichia coli

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Abstract
A purE::lac fusion strain of E. coli was isolated by using a special Mu phage. In the presence of adenine (100 .mu.g/ml), .beta.-galactosidase synthesis was repressed by 90%. .beta.-Galactosidase activity could be detected 6-8 min after the removal of adenine and increased linearly for at least 20 min. purR- mutants were isolated and synthesized 1.7- to 1.8-fold-higher levels of .beta.-galactosidase compared with purR+ cells. Azaserine derepressed purE transcription approximately 1.7-fold by lowering purine nucleotide pools. Glutamine and pyrimidine supplementation or starvation had no effect on purE transcription. A comparison of the rate of de novo purine biosynthesis and purE transcription indicated that the in vivo rate of de novo purine biosynthesis was more sensitive to the inhibitory effects of adenine than was transcription at the purE locus.

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